Overload relay



Feb. 26, 1935. v G. o. wluws' 1,992,595

OVERLOAD RELAY Filed May. 14, 19254 vDUE/5V ELM/7775 Patented Feb. 26, 1935 1,992,595 ovEn'LoAn RELAY Gustav 0. Wilms, Milwaukee, Wis., assignor to Allen-Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Application May 14, 1934, Serial No. 725,447

20 Claims. (01. 200-424) UNITED STATES PATENT OFFICE This invention relates to new and useful im- Fi ure 1 is a persp c ive view of an ov provements in overload relays for electrical .conrelay embodying this invention; Y trol equipment and has as an object to provide Figure 2 iS a horizontal Section view take a thermal overload relay, which will afford accut l h Figure 1 on the Plane of t e line 2- 5 rate and reliable motor protection against sus- Figure3 isavertical section view taken throu 5 tained' overloads. Figure 1 on theplane of the line 3-3; and

Another object of this invention is to provide u e] 4 iS a enlarged detail Section View an overload relay which is particularly adaptable lie-ken n the plane of the line 0f u e for use with the starting switch shown and de- Referring now mo e particularly to e a m- 10 scribed in the copending application of Gustav D ying drawin in Which like numerals indil0 0. Wilms and Albert J. Dawe, Serial'No. 710,656, t l pa ts throu h ut th s veral vi ws, the filed February 10, 1934. numeral 5 designates a supporting base for the Another object of this invention is to provide relay, Which is preferably molded Of a Suitable a v ad relay of the type having tripping insulating material such as a phenol condensalb mechanism held in an operative position by a lien predlletl5 pawl engaging a ratchet secured to a supporting e base has a ront wall 6 and a rear Wa stem by solder or some other fusible alloy which connected y a Side Well The side wall 3 is melts upon the occurrence of an overload to reprovided with a boss 9 on its outer side throu lease the tripping mechanism, in which the which two holes 10 extend for the reception of rious elements are substantially enclosed and so attaching Screws w by W c the as .20 arranged and associated as to afiord maximum y be secured t 3 Suitable pp i Structurecompactness and ruggedness of construction. h heads of the attaching r w are disposed Another object of this invention is t provide a in wells 11 formed on the front of the side wall thermally responsive overload relay so construct- 8 adjacent the rear wall 7 so that the attachin ed that the stress of shear on the fusible alloy, screws are adequately p tected f om co tact 25 which provides the temperature responsive elewith y p Of the Switch mechanism new to ment, small to insure accurately tim d t i i be described, which is mounted on the side wall 8.

A fur her object of this invention is to provide The Switch mechanism o p s two s nan overload relay of the character described, ary contacts 12 and 13 rigid y mounted on the wherein the ratchet, which is releasably held in Side Wall by rivets 14 and 15 p t v y, Whic 30 1 its operative position by a fusible alloy turns on also pass through, terminals 16 and p an axis perpendicular to the axis about which y, 0n t e b f he S Wall t imulthe contactor actuator or tripping finger turns taneously secure the stationary contacts and their so that the relay may be conviently mounted on terminals to iJhe b and lectrically o ec 5 a switch structure with its heater stem, on which the Samethe ratchet is secured, pointing to the front of A best Shown in Figure 2, the ut ends of the switch structure, and at the same time, the the terminals are t laterally a d p i tripping and resetting motion is in a plane pen with screws 18 for attachment of conductor wires pendicular to the front of the switch structure. therete- These stationary contacts ou ei with th above and other object in View which terminals 16 and 1'7 are adapted for connection 40 appear as the description proceed my i in series the magnetizing Coil circuit Of the vention resides in the novel construction, 'combi- Switch or any other electrical circuit to be nation and arrangement of parts substantially as A moYable contactor 19 is Provided to electrihereinafter described and more particularly de- Cally brldge the fiontacts 12 and The 0011- fined by t appended claims, t being understood tactor 19 is pivotally mounted as at 20 On the 45 that such changes in the precise embodiment of ireeend of lfiver which is movable to carry the hereindisclosed invention may be made as gfi Into and out of {Engagement i come within the Scope of the claims e s ionary contacts. The pivotal connection In the accompanying drawing, I have 20 permits the contactor to adjust itself to the trated one complete example of the physical emstatlom'ry contacts' so The lever 21, which is formed of insulatin mabodiment of my invention constructed according terial is pivot-any mounted on a pivot g 22 to e e e I have so devised for the secured to the side wall a, as best illustrated in pra ti al a p at f the p m ip s th and. Figure 2. Also pivotally mounted on the post 22' in which: is a second lever 23 stamped from bendable metal against the lever 21 and its other end engaging the lever 23, yieldably urges the lever 21 in a counter-clockwise direction to engage its contactor with the stationary contacts 12 and'13.

The lever 23 is yieldably urged in a clockwise direction by a compression spring 26 having one end bearing against the rear wall 7 and its other end engaging an upturned lip 2'? formed on the lever 23. This tendency toward clockwise rotation on the part of the lever 23 is transmitted to the lever 21 through lugs 28 bent inwardly from the two arms 24. of the lever 23 for engagement with an extension 29 on the lever 21 projecting down beneath the pivot stem, so that whenever the lever 22 is moved by the spring 26, the lever 21 is likewise swung about the axis of the pivot stem 22 to carry its contactor 19 to an inoperative position illustrated in dotted lines in Figure l.

To hold the mechanism in a switch closing position, the lever 23 carries a spring pawl 30, which projects toward the front wall 6 and has its outermost end 31 bent laterally for engagement with a ratchet 32. The ratchet 32 is fixed on the inner end 33 of a shaft 34. by solder 35 or any other suitable fusible material. The shaft 34 is carried by the front wall 6 of the base with its opposite ends projecting forwardly and rearwardly therefrom. At its point of attachment to the base, the shaft 34 is provided with a cupped flange 36 to receive the hub 37 of the ratchet with sufficient clearance to accommodate the solder 35.

The outer end 38 of the shaft 34 which projects forwardly beyond the front wall 6 has a heating element 39 encircling it. The ends of this element, which in the present instance, is illustrated as a coil of resistance wire, are secured to terminals 40 by screws 41 so that the heating element may be quickly taken off and replaced without the use of any tools except a small screw driver.

Terminal screws 42 are also carried by the termi-,

nals 40 for connecting the heating element in the proper control circuit.

It is observed that the shaft 34 is hollow. This increases the rapidity of the conduction of heat thereby to the solder or fusible material 35. After the occurrence of an overload in the circuit in which the heater coil is connected and the consequent tripping of the, relay, the solder again quickly sets to secure-the ratchet to the shaft and permit resetting.

It is to be noted that the spring pawl 30 affords a comparatively long lever for moving the mechanism to its switch closing position and holding it there. Consequently, the stress or shear on the fusible alloy which secures the ratchet to the shaft 34 is small to insure accurately timed response in the event of an overload.

Resetting after an overload, may be quickly effected by swinging the lever 23 about its mounting stud in a counter-clockwise direction, and for this purpose, a lateral arm 45 is secured to the lower end of the lever 23 to project beyond the side wall 8 as illustrated. in Figure 3. Any suitable mechanism may be provided for engaging this lateral projection Y45 and pushing it inwardly to effect the resetting of the relay.

A protecting cover 46 may be secured across the space between the front and rear walls as illustrated.

The operation of the device may be briefly summarized as follows: The relay contacts 12 and 13, which are bridged by the contactor 19 are in series with the magnetizing coil circuit of the switch with which the relay is associated. These contacts are normally held closed by the pawl 30 engaging the ratchet 32, and the ratchet, as stated, is soldered to the shaft 34, which is surrounded by the heater element.

If an overload current flows through the heater element, the shaft 3% overheats and melts the solder, Such melting permits the ratchet to turn and free the pawl which in turn opens the relay contacts and permits the main switch to trip. With the main switch tripped, the heater element ,is taken out of the circuit and the solder freezes or sets to again hold the ratchet secure on its shaft. The relay contacts can then be reset and the starter is again ready for action. This performance may be repeated any number of times without affecting the accuracy of the relay.

As illustrated in the aforesaid copending application, the relay is preferably mounted with its front wall 6 facing the front of the switch structure with. which it is associated, and the heater stem projecting forwardly therefrom.

This position of the unit facilitates the removal and application of the heater element. It also facilitates resetting as the resetting lever turns about an axis disposed at right angles to the axis of the heater stem and thus moves in a plane perpendicular to the front of the switch structure. Hence, a normal inward motion, as obtained by a push button, is all that is necessary to reset the relay.

While the relay has been defined as directly controlling the opening and closing of a switch to be connected in series with the magnetizing coil ofan electromagnetic switch, it is also readily applicable to a hand operated starting switch in which the switch is held closed by a latch releasable by tripping of the relay. When so used, the contactors 12 and 13 and the associated contactor are of course omitted, but in other respects, the relay embodies the sameconstruction as shown and described.

From the foregoing description taken in connection with the accompanying drawing, it will be readily apparent to those skilled in the art,

. that this invention affords an overload relay for motor protection which is compact and rugged in construction; and that all parts thereof are readily accessible, particularly the heater element, so that removal and attachment thereof is an extremely simple matter requiring no tool other than a screw driver.

What I claim as my invention is:

1. An overload relay comprising a base having angularly disposed walls, a switch mounted on one wall including a movable switch member yieldably biased to its switch opening position, and means to hold said switch actuating member in its position closing the switch comprising a heat conducting shaft carried by the other wall With its opposite ends projecting to opposite sides thereof, a ratchet wheel fixed on one end of said shaft by a fusible binder, a pawl connected with said switch member and engageable with said ratchet wheel, and a heater element in close proximity to the other end of the shaft adapted to heat said shaft and release the ratchet upon the occurrence of a predetermined temperature rise at said heater element.

2. In an overload relay, a supporting base havmg connected walls disposed at angles toeach other, a switch mounted on one wall and including a stationary contact and a movable contactor engageable therewith, a lever also mounted on said wall and operable to move the contactor to its switch opening position, means yieldably urging said lever to its switch opening position, and means to hold the lever against movement to its switch opening position until the occurrence of an overload condition in a circuit with which the relay is associated comprising a heat conducting shaft mounted in the other wall of the base with its opposite ends projecting to opposite sides thereof, a ratchet fixed to the inner end of said shaft by a fusible binder, a pawl connected with said lever. and engageable with the ratchet to hold the lever in its switch closing position as long as the ratchet is secure on the shaft, and a heater element adjacent the outer end of the shaft to transmit heat thereto and release the ratchet wheel upon the occurrence of a predetermined temperature rise in said heater element. I

3. In an overload relay, a base, a switch mounted on the base and including a movable switch arm mounted to ,swing about a fixed axis, a lever associated with the switch arm and also mounted to turn about a fixed axis, a spring yieldably urging the lever to a position holding the switch arm in a switch opening position, and means to hold the lever against actuation by said spring comprising, a shaft mounted from the base with its axis disposed substantially perpendicularly to the axes of the pivots of the switch arm and said lever, a ratchet fixed on one end of said shaft by a fusible binder, a pawl connected with said lever and engaging said ratchet to hold the lever in its switch closing position against the action of the spring as long as the ratchet is fixed to the shaft, and a heater element to heat the shaft and release the ratchet.

4. In an overload relay, a base, a pair of stationary contacts mounted on the base, a switch arm pivotally mounted on a base to turn about a fixed axis, a contactor carried by the switch arm to bridge the stationary contacts, an actuator lever mounted on the base to turn about said fixed axis about which the switch arm turns, a light spring connecting the lever and the switch arm to yieldably urge the switch arm about said fixed axis toward switch closing position, a heavy spring engaging the lever to yieldably urgethe lever in one direction about said fixed axis, a connection between the lever and the switch arm whereby such motion of the lever moves the switch arm to switch opening position, a spring finger carried by said lever, and a releasable abutment engageable by said spring finger to hold the lever against actuation by its spring in a position permitting closure of the switch.

5. In an overload relay of the character described, a base, a switch contact carried by the base, a contactor engageable with the contact, a pivot post carried by the base, a switch arm mounted to turn on said pivot post and carrying the contactor, an actuator lever also mounted to turn on said pivot post, a connection between the lever and the switch arm whereby movement of 4 the lever in one direction moves the switch arm to a switch opening position, a spring to yieldably urge the lever in said direction, and thermally releasable means to hold the lever against actuation by said spring.

6. In an overload relay of the character described, a base, a switch contact carried by the base, a contactor engageable with the contact, a pivot post carried. by the base,-a switch arm mounted to turn on said pivot post and carrying the contactor, an actuator lever also mounted to turn on said pivot post, a connection between the lever and the switch arm whereby movement of the lever in one direction moves the switch arm 'to a switch opening position, a spring to yieldably urge the lever in said direction, a spring finger carried by the lever and extending laterally therefrom, a heat conducting shaft mounted with its axis perpendicular to the axis of said pivot post and a ratchet wheel fixed on said shaft by a fusible binder with its toothed periphery arranged for engagement by the spring finger, whereby said lever is held against actuation by its spring as long as the ratchet wheel is secure on its shaft.

7. In an overload relay, a switch mechanism including a member rotatably mounted and yieldably urged toward a switch opening position, a heat conducting shaft mounted with its axis disposed angularly with respect to the axis of rotation of said member, a ratchet wheel fixed to said shaft by a fusible binder, and a pawl carried by said member and arranged to move in a plane substantially parallel with the axis of said shaft with its outer end portion traversing the toothed periphery of the ratchet wheel to be engageable therewith and to thereby hold said member against movement to its switch openingposition as long as the ratchet wheel remains fixed to said shaft.

8. In an overload relay, a switch mechanism including a member rotatably mounted and yieldably urged toward a switch opening position, a heat conducting shaft mounted with its axis disposed angularly with respect to the axis of rotation of said member, a ratchet wheel fixed to said shaft by a fusible binder, and a spring finger fixed to said member and mounted to swing about the axis of rotation of said member in a plane substantially parallel to the axis of said shaft with its outer end arranged to wipe "across the side of the toothedperiphery of the ratchet wheel and to engage a tooth thereof to restrain said member against movement to its switch opening position as long as the'ratchet wheel remains fixed to said shaft.

9. In an overload relay, a base, a switch contact carried by the base, a contactor engageable therewith, a pivot post fixed to the base, a switch arm mounted to turn about the pivot post and carrying the contactor, a lever "having spaced arms journalled on said pivot post on opposite sides of said switch arm, a torsion spring encircling the pivot post with one end engaging the switch arm and its other end engaging one arm of said lever to yieldably urge the switch arm to switch closing position, a connection between said lever and switch arm whereby movement of the lever in one direction about the pivot post carries the switch arm to its switch opening position, a spring having one end disposed between the arms of the lever and bearing against an abutment thereon to yieldably urge the lever in said direction, and a thermally releasable catch to restrain said lever against actuation by its spring.

10. In an overload relay of the character described, a base, a pair of stationary contacts mounted on the base, and a movable contactor to bridge the contacts, a pivot post carried by the base, a switch arm mounted to turn about the pivot post, means pivotally mounting the contactor from said switch arm to allow the contactor to adjust itself to the contacts upon movement of the arm toward switch closing position, an actuator lever having spaced arms also pivotally mounted on said pivot post at opposite sides of said switch arm, a connection between said lever and the arm whereby movement of the lever in one direction about the pivot post swings the switch arm to its switch opening position, a compression spring having one end bearing against an abutment on the lever to yieldably urge said lever in said direction, a spring finger carried by the lever projecting therefrom, and a releas able catch engageable by said spring finger to hold the lever against actuation by its counores-- sion spring.

ii. in an overload relay of the character described, a base, a pair of stationary contacts mounted on the base, and a movable contactor to bridge the contacts, a pivot post carried by the base, a switch arm mounted to turn about the pivot post, means pivotally mounting the contactor from said switch arm to allow the contactor to adjust itself to the contacts upon movement of the arm toward switch closing position, an actuator lever having spaced arms also pivotally mounted on said pivot post at opposite sides of said switch arm, a connection between said lever and the switch arm whereby movement of the lever in one direction about the pivot post swings the switch arm to its (switch opening posi tion, a compression spring having one end bearing against an abutment on the lever to yieldably urge said lever in said direction, a spring finger carried by the lever projecting therefrom, and a releasable catch engageable by said spring finger to hold the lever against actuation by its compression spring, said releasable catch comprising a heat conducting shaft carried by the base, and a ratchet wheel fixed on the shaft by a fusible binder with its toothed periphery arranged to be traversed and engaged by the outer end portion of the spring finger.

12. In an overload relay, a base of insulating material having a side wall and spaced front and rear walls projecting angularly therefrom, switch mechanism mounted on the side wall and including a lever mounted to turn about an axis parallel with the front and rear walls and positioned therebetween, a compression spring engaging the rear wall and said lever to yieldably urge the lever to a switch opening position, a

' heat conducting shaft carried by the front wall,

a ratchet wheel fixed to the shaft by a fusible binder, and a spring finger carried by said lever with a portion thereof arranged to traverse and engage the toothed periphery ofsaid ratchet wheel to secure the lever against actuation by its spring as long as the ratchet wheel remains fixed to its shaft.

13. In an overload relay, a base'of insulating material having a side wall and a front wall substantially perpendicular thereto, switch instrumentalities mounted on the side wall behind the front wall and including a member yieldably biased to switch opening position, and thermally releasable means to secure said member against movement to switch opening position comprising, a heat conducting shaft carried by the front wall with its ends projecting forwardly and rearwardly thereof, a ratchet wheel fixed to the rear end portion of said shaft by a fusible binder, a pawl connected with said member and engageable with the ratchet wheel to hold the member against movement to its switch opening position as long as the ratchet wheel is fixed to the shaft,

a heater element in juxtaposition to the forwardly extending end portion of the shaft, and terminals for said heater element on the front face of said front wall and to which the ends of the heater element are detachably secured.

14. In an overload relay, a supporting base of insulating material having a side wall and a front wall substantially perpendicular thereto, switch instrumentalities carried by the side wall and behind the front wall and including switch contacts, terminals for the switch contacts on the outer face of said side wall having laterally bent portions in juxtaposition to the front wall to be readily accessible for the attachment of wires thereto, said switch mechanism also including a member yieldably urged to a switch opening position, means to hold said member against movement to its switch opening position comprising a heat conducting shaft carried by the front wall with an end portion projecting forwardly from the face of the front wall, a ratchet wheel fixed to the inner end portion of the shaft by a fusible binder, a pawl connected with said member and engageable with the ratchet wheel to hold said member against movement to its switch opening position as long as the ratchet wheel is secured to the shaft, a heater element in juxtaposition to the forwardly projected end portion of the shaft to influence the same thermally and release the ratchet wheel, and terminals for said heater element mounted on the front face of the front wall and to which the ends of the heater element are readily detchably secured.

15. In an overload relay, a supporting base of insulating material having a side wall and a front wall substantially perpendicular thereto, switch instrumentalities carried by the side wall and behind the front wall and including switch contacts, terminals for the switch contacts on the outer face of said side wall having laterally bent portions in juxtaposition to the front wall to be readily accessible for the attachment of wires thereto, said switch mechanism also including a member yieldably urged to a switch opening position, means to hold said member against movement to its switch opening position comprising a heat conducting shaft carried by the front wall with an end portion projecting forwardly from the face of the front wall, a ratchet wheel fixed to the inner end portion of the shaft by a fusible binder, a pawl connected with said member and engageable with the ratchet wheel to hold said member against movement to its switch opening position as long as the ratchet wheel is secured to the shaft, a heater element in juxtaposition to the forwardly projected end portion of the shaft to ihfluence the same thermally and release the ratchet wheel, terminals for said heater element mounted on the front face of the front wall and to which the ends of the heater element are readily detachably secured, and means connected with said yieldably urged member and arranged to receive inward thrust perpendicular to the front wall for re-setting the relay.

it. In an overload relay, a supporting base, a

pivot post carried by the base, a member to be moved upon the occurrence of an overload, said the toothed periphery of the ratchet wheel upon movement of the lever about the pivot post and to engage a tooth thereof toreleasably hold said member against actuation by its yieldable urging means as long as the ratchet wheel remains fixed to its shaft.

1'7. In an overload relay, a supporting base having angularly disposed walls, a pivot post carried by one wall, a member mounted to turn about said pivot post, yieldable means urging said member in one direction of rotation, a heat conducting shaft mounted on the other of said angularly disposed walls with its axis substantially perpendicular to the axis of the pivot post, a ratchet wheel fixed to said shaft by a fusible binder, and a spring finger extending from said member and having a part arranged to wipe across the side of the toothed periphery of the ratchet wheel and to engage a tooth thereof to restrain said member against movement by its yieldable urging means as long as the ratchet wheel remains fixed to said shaft.

18. In an overload relay, a base, a pivot post on the base, a member mounted to turn on said post, a springyieldably urging the member in one direction, a heat conducting shaft mounted on the base with its axis substantially perpendicular to theaxis of the pivot post,'a ratchet wheel fixed to said shaft by a fusible binder, and a long arm carried by said member with its outer'end arranged to wipe across the side of the toothed periphery of the ratchet wheel and to engage a tooth thereof to restrain said member against movement by the spring as long as the ratchet wheel remains fixed to the shaft, and a heater element in juxtaposition to the shaft to heat the shaft and melt the fusible binder.

19. In an overload relay, a base having a front wall and'a side wa1l, a pivot post mounted-on the. side wall with its axis parallel to the front wall, a member to be moved upon the occurrence of an overload pivotally mounted on said post to swing in a plane of movement perpendicular to the front wall and parallel to the side wall, a spring to urge said member toward the front wall, a heat conducting shaft mounted on the front wall with its axis perpendicular to the front wall and to the axis of the pivot post, a ratchet wheel fixed to said shaft by'a fusible binder, a spring finger carried by said member with its outer end arranged to wipe across the side of the toothed periphery of the ratchet wheel and to engage a tooth thereof to restrain said member against movement as long as the ratchet wheel remains fixed to said shaft, a heater element mounted on the front wall of the base in juxtaposition to the shaft to transmit heat thereto and melt the solder, and means on said member adapted to receive direct inward thrust from the front of the relay for moving the same against the action of its spring. 20. In an overload relay, a spring adapted to be placed under stress to afford potential force for actuating a member to be moved upon the occurrence of an overload, a lever pivoted to turn about a fixed axis and arranged to releasably hold the spring under stress and to be actuated by the spring upon its release, so that the lever provides a medium for transmitting the motion produced by release of the force of the spring to such mem ber, and means to releasably secure the lever in its position holding the spring under stress comprising a heat conducting shaft mounted with its axis perpendicular to the axis about which the lever turns, a ratchet wheelfixed to the shaft by a fusible binder to be freely rotatable on the shaft upon the occurence of a predetermined temperature rise thereat, and an arm carried by said lever and having a part arranged to traverse and engage the toothed periphery ofsaid ratchet wheel to hold the lever in its spring securing position as long as the ratchet wheel remains fixed to the shaft.

GUSTAV O. WILMS. 

